A cable window lifter for a window which can be lowered in window pocket of a vehicle is disclosed in German Patent Publication DE 81 32 167 U1. The cable window lifter has a guide rail disposed in the direction of movement of the window, along which a slide element is disposed displaceable in the longitudinal direction and which acts on the lower window edge and is connected with a driving cable of the cable window lifter. The driving cable is brought over deflection pulleys disposed on the upper and lower ends of the guide rail to a driving unit. The driving unit comprises a drive housing with a cable drum disposed therein for receiving the driving cable and a drive shaft. The drive shaft can be connected with a hand crank for manual operation of the cable window lifter or with a motor drive. Customarily the driving cable is disposed in a Bowden case fastened to Bowden supports of the drive housing. The driving cable itself is connected to the cylindrical surface of the cable drum and is connected in such a way that, when the drive shaft is moved in one or the other direction of rotation, the driving cable is wound onto or unwound from the cable drum, causing the carrier connected with the window and guided on the guide rail to be moved upward or downward.
The drive shaft for the cable drum can be disposed outside the longitudinal axis of the cable drum and can be connected with the cable drum via a gear connection. Alternatively, it is possible to provide the movement of the cable drum via a pinion gear disposed in the free cylindrical interior of the cable drum and engaging an internal gear of the cable drum. On one of its cylindrical front faces the pinion gear is connected via a pinion pin with a bearing bore disposed in the housing wall of the drive housing, and on its other front side with a drive shaft or directly or via engaging dogs with a hand crank.
If the pinion gear is driven in one or the other direction of rotation, a turning of the cable drum in the one or the other direction takes place via the connection of the pinion gear teeth with the internal gear of the cable drum. This causes the end of the driving cable, which is brought via the one Bowden support on the drive housing to the cable, to be wound up, and the cable end, which is brought via the other Bowden support on the drive housing to the cable drum and connected therewith, to be unwound.
The forces occurring in the cable window lifter described above during raising and lowering the window also act on the teeth of the pinion gear and the cable drum. As a result, in cases of overload, for example because of a window which moves tightly because of friction or is jammed, the pinion gear teeth are pushed out of the internal gear of the cable drum, so that the meshing between pinion gear and cable drum is severed. This can cause destruction of the teeth of the driving unit or breakage of the pinion bearing, due to the large loads on the bearing of the pinion gear so that in either case the driving unit is unable to function.
It is, therefore, the object of the invention to provide a cable window lift of the species mentioned at the outset, by means of which the engagement of the pinion gear teeth with the internal gear of a cable drum is assured with small expenditure even in cases of overload, and which also assures an improved running quality of the gear elements of the driving unit during normal operation.